1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly to an apparatus and method for data transmission/reception in a mobile telecommunication system.
2. Description of the Related Art
In general, wireless communication systems have been developed for terminals that cannot be connected to a fixed wired network. The representative wireless communication systems include mobile telecommunication systems, for example, a Wireless Local Area Network (LAN) system, a Wireless Broadband Internet (WiBro) system, a Mobile Ad Hoc system, an Ultra Mobile Broadband (UMB) system, etc. Different from normal wireless communication systems, the mobile communication system is based on the mobility of the user. The ultimate object of the mobile telecommunication system is to enable information media to be exchanged through a Mobile Station (MS), such as a mobile phone, a Personal Digital Assistant (PDA), and a wireless pager, regardless of time and space, that is, regardless of “when,” “where,” and “to whom.” With the rapid development of communication technology, current mobile telecommunication systems are providing not only ordinary voice communication services, but also high rate data services which enable transmission of large-capacity digital data, such as moving images, as well as the transmission of e-mail or still images, by using a mobile station.
One representative example of current mobile telecommunication systems providing high rate data services is an Orthogonal Frequency Division Multiplexing (OFDM) system. According to the transmission scheme of the OFDM system, a serially-input symbol sequence is converted into parallel signals, and the parallel signals are transmitted through a plurality of mutually orthogonal subcarriers. The OFDM scheme has come into the spotlight since the beginning of the 1990's, according to the development of the Very Large Scale Integration (VLSI) technology.
According to the OFDM scheme, data is modulated by means of multiple subcarriers, and the sub-carriers maintain the orthogonality between them, so that the OFDM scheme is more robust against frequency selective multipath fading channel, and is more proper for the high rate packet data services, such as a broadcasting service, than the existing single carrier modulation scheme.
Generally, the OFDM system may classify Voice over IP (VoIP) users into a plurality of groups according to different distances from a base station and manage the VoIP users according to each group in order to efficiently support the VoIP users.
With respect to the VoIP users grouped as described above, resources are assigned by transmitting one message to each group, instead of transmitting one Forward Link Assignment Message (FLAM) to each user.
Through such a method, the general OFDM system can prevent the base station from using a large amount of power in order to enable all users to see FLAMs transmitted through a Forward link Shared Control CHannel (F-SCCH).
Resources assigned to group users by a specified message can be recognized through a bitmap. Through such a bitmap, each definite resource, that is, one Block Resource Channel (BRCH) or one Distributed Resource CHannel (DRCH), is assigned to each user. However, the method of grouping the users by means of a bitmap has a problem in that resources assigned to the groups are not fully used by the group users.